I have been struggling with the same problem, but now I have made a solution that works for me so far.
I created a class, ComWrapper, that I wrap the Excel COM object in. It automatically wraps every nested object and call in ComWrapper, and unwraps them when they are used as arguments to function calls or assignments to wrapped objects. The wrapper works by catching the "Call was rejected by callee"-exceptions and retrying the call until the timeout defined at the top is reached. If the timeout is reached, the exception is finally thrown outside the wrapper object.
Function calls to wrapped objects are automatically wrapped by a function _com_call_wrapper, which is where the magic happens.
To make it work, just wrap the com object from Dispatch using ComWrapper and then use it as usual, like at the bottom of the code. Comment if there are problems.
import win32com.client
from pywintypes import com_error
import time
import logging
_DELAY = 0.05 # seconds
_TIMEOUT = 60.0 # seconds
def _com_call_wrapper(f, *args, **kwargs):
"""
COMWrapper support function.
Repeats calls when 'Call was rejected by callee.' exception occurs.
"""
# Unwrap inputs
args = [arg._wrapped_object if isinstance(arg, ComWrapper) else arg for arg in args]
kwargs = dict([(key, value._wrapped_object)
if isinstance(value, ComWrapper)
else (key, value)
for key, value in dict(kwargs).items()])
start_time = None
while True:
try:
result = f(*args, **kwargs)
except com_error as e:
if e.strerror == 'Call was rejected by callee.':
if start_time is None:
start_time = time.time()
logging.warning('Call was rejected by callee.')
elif time.time() - start_time >= _TIMEOUT:
raise
time.sleep(_DELAY)
continue
raise
break
if isinstance(result, win32com.client.CDispatch) or callable(result):
return ComWrapper(result)
return result
class ComWrapper(object):
"""
Class to wrap COM objects to repeat calls when 'Call was rejected by callee.' exception occurs.
"""
def __init__(self, wrapped_object):
assert isinstance(wrapped_object, win32com.client.CDispatch) or callable(wrapped_object)
self.__dict__['_wrapped_object'] = wrapped_object
def __getattr__(self, item):
return _com_call_wrapper(self._wrapped_object.__getattr__, item)
def __getitem__(self, item):
return _com_call_wrapper(self._wrapped_object.__getitem__, item)
def __setattr__(self, key, value):
_com_call_wrapper(self._wrapped_object.__setattr__, key, value)
def __setitem__(self, key, value):
_com_call_wrapper(self._wrapped_object.__setitem__, key, value)
def __call__(self, *args, **kwargs):
return _com_call_wrapper(self._wrapped_object.__call__, *args, **kwargs)
def __repr__(self):
return 'ComWrapper<{}>'.format(repr(self._wrapped_object))
_xl = win32com.client.dynamic.Dispatch('Excel.Application')
xl = ComWrapper(_xl)
# Do stuff with xl instead of _xl, and calls will be attempted until the timeout is
# reached if "Call was rejected by callee."-exceptions are thrown.
